Roll libxml to 0f3b843b3534784ef57a4f9b874238aa1fda5a73

Follows recipe in
https://cs.chromium.org/chromium/src/third_party/libxml/chromium/roll.py?l=25

Bug: 727039
Change-Id: Iad741672da34aa2abdd4e5566cb12c8840e0831d
Reviewed-on: https://chromium-review.googlesource.com/698864
Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Commit-Queue: Scott Graham <scottmg@chromium.org>
Cr-Commit-Position: refs/heads/master@{#506245}
34 files changed